Hi Matthew. Brand is such a deep, misunderstood and maligned word these days.
IMHO, I'd start here: Ditch the concept of "re-branding." A brand is a symbol of what is, not something applied to a product or service to make it appealing to the market. In that sense, you can't actually "re-brand" anything ... your product already has its own essence and your job is to uncover it. :-)
So, come to terms with what you envision and how that aligns with the marketplace AND its current impression of your business. Fill in the gaps, tweak the dials of your offering so that it's all authentic and meets market needs.
Then, when you have the full picture, you can begin to understand how to best present that value to the market, in terms of customer experience style, substance, communication, etc.
There are some seminal books on what brand really is and what to do about it. A quick search on "best book about brand" will yield tons of results. Pick a few that speak to you.
Hope that helps.